A spokesperson for Irish Water says she does not know how much public money was lost in the PPS number debacle.
Elizabeth Arnett says the utility is currently destroying the numbers it received, and that process could be completed by the end of the month.
The utility says some 56% of the population have so far registered for water.
They are reminding people to confirm their details with them by the deadline of February 2nd.
Irish Water says a household with one adult will be charged no more than €160 per year - while a household with two or more adults will be charged no more than €260 per year.
Water services for children are free and every household registered with will qualify to apply for a water conservation grant of €100 per year.
The PPS requirement was scrapped by the environment minister in November, after a public backlash over privacy concerns.
But Ms Arnett told the Pat Kenny Show here on Newstalk that the company still does not know how much it has cost the taxpayer.
